The second free publication I'm featuring is actually a magazine, not a book: Bulletin of Primitive Technology, first issue. At 52 pages, though, it rivals much of what is being published today as e-books. The only thing that makes it a magazine is the variety of articles. Some are deeply philosophical, others are intensely practical. The magazine is no longer being published, but the material has been collected into several books put out by the Society for Primitive Technology (which are not free).